Human blood coagulation factor VII circulates in blood as a precursor of a serine-protease. The expression of the proteolytic activity of factor VII, or its activated form, factor VIIa, occurs as a result of complex formation with a specific cell surface glycoprotein designated as tissue factor. While many of the steps involved in the coagulation cascade have been studied on a molecular basis, little is known as to how the activity of factor VII towards protein substrates is augmented several order of magnitude by complex formation with tissue factor in the presence of calcium ions, and how this activity, once formed, is regulated in vivo. The specific aims of the proposed research address the issues of: (a) the interaction, procoagulant activity and substrate specificity of human factor VIIa on cultured endothelial cells in both the quiescent and perturbed states, (b) the intrinsic proteolytic activity of zymogen factor VII and mechanisms of its proteolytic activation in vivo, and (c) the biochemical properties of plasma-derived, recombinant wild-type and site-specific mutants of human factor VII. One of the long-range goals of this project is to obtain a better understanding of the relative rates of the factor VIIa-tissue factor mediated activation of factor IX and factor X as it occurs during hemostasis. Another, equally important goal of this project is to identify the protease(s) and any cofactor(s) necessary for optimal proteolytic activation of zymogen factor VII in vivo and elucidate the mechanism of this reaction. The proposed research will utilize standard protein isolation and characterization procedures, established coagulation assays, currently employed tissue culture techniques and protocols, affinity chromatography and amino acid sequence methodology. Hopefully, information gathered in this study will provide insight into the precise role of factor VII in both normal and pathological states, and inferences as to the role of extrinsic coagulation in the pathogenesis of various thromboembolic disorders including transient cerebral ischemic attacks, vein and artery occlusion, atherosclerosis, and deep venous thromboembolism. It is further hoped that, based on the results of these studies, future therapies will evolve that restrict the deleterious effects of tissue factor and be effective in the prophylaxis of thromboembolic disorders.